Injecting skeletal muscle- or adipose tissue-derived mesenchymal stem cells into the heart muscle of laboratory rats with myocardial infarction led to improvement in left ventricle function and smaller infarct size in the animals, according to a Norwegian study published in Cell Transplantation. Injection of the cells one week after acute myocardial infarction yielded better outcomes compared with infusions of cell culture medium only, researchers said. There is still a need to address several concerns regarding the method, such as whether MSCs from different organisms would yield different functional outcomes, researchers said.